1. Field of the Invention
The present invention relates to a wet type color electrophotographic copying machine which is provided with a plurality of color developing devices, and in particular, to a wet type color electrophotographic copying machine in which a color turbidity can be eliminated appreciably by the enhancement of a removal effect of a surplus developer removing device thereof.
2. Prior Art
Generally, for such wet type color electrophotographic copying machine, surplus developer removing devices, e.g., as disclosed in Japanese Provisional Patent Publication No. 56 (1981)-21168 are known in the art.
This kind of surplus developer removing device is provided with a developer recovery blade between each color developing device and an air knife device disposed behind that, in order to return some escaped developer to near the blade, A small clearance is also provided between the tip of the developer recovery blade and an image carrying-surface, in order that a toner image on the surface is not put out of order by the tip of the blade. Surplus developer remaining on the image-carrying surface is mostly recovered by the blade. Surplus developer brought out behind the blade with the image-carrying surface is returned to the area near the tip of the blade, by means of air blowing from the air knife device, and is then recovered by the blade.
However, the above-mentioned prior removing device is difficult to set up so as to maintain a uniform clearance between the image-carrying surface and the tip of the blade disposed widthwise thereof. The term "widthwise" is the direction intersecting the direction of the relative movement therebetween. Therefore, the prior art removing device has a problem in that due to the non-uniform clearance between the tip of the blade and the image-carrying surface a stripe-shaped unevenness is generated on the image in the direction of its movement.
It is also known in the art that a developer squeezing roller unit may be used to advantage instead of the developer recovery blade, e.g., as disclosed in Japanese Patent Publication No. 58 (1983)-47707). Such a squeezing roller unit includes at least two contact rollers, disposed so as to be in contact with the image-carrying surface at both ends thereof, and a small diameter roller arranged between the contact rollers so as to have a uniform clearance between the small diameter roller and the image-carrying surface.
However, in known copying machines in which a plurality of developing heads of the color developing devices are constructed so as to be able to approach to and recede from the image-carrying surface, the developer recovery blade or the developer squeezing roller unit set up in each color developing device leaves the image-carrying surface when the color development is completed. Consequently surplus developer held in the above-mentioned clearance still remains at the boundary area of the image-carrying surface where no images exist (hereinafter, referred to a "non-image area"), the remaining developer probably causes a color turbidity in an image developed in the next color developing process.